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Periodic Extinctions Have Been the Rule for Life on Earth

Periodic Extinctions Have Been the Rule for Life on Earth. Extinction has been wide spread. Cambrian - 80% of families - > 90% of species Permian - 60% families 90% species Cretaceous - 20% families > 50% species.

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Periodic Extinctions Have Been the Rule for Life on Earth

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  1. Periodic Extinctions Have Been the Rule for Life on Earth • Extinction has been wide spread. • Cambrian - • 80% of families - • > 90% of species • Permian - • 60% families • 90% species • Cretaceous - • 20% families • > 50% species

  2. Is it possible that life has not been a process of ever expanding diversity? • Could speciation and diversification be a process of periodic extinction and subsequent reradiation?

  3. So How Old is the Earliest living Organism? Gunflint Chert in Banded Iron formation -- Lake Superior about 1.9 b.y. old

  4. Stromatolites - bacterial tufts Western Australia & elsewhere Contain fossil bacteria (cyanbobacteria) 3.5 - 4.0 b.y. old

  5. For many years 5 kingdom system held

  6. New Techniques have discovered much more diversity, leading to revision of classification

  7. Bio 103 home

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